Proven procedures for fertilizing rhesus monkey oocytes in vitro and sustaining development through early cleavage stages will be used to examine fundamental aspects of primate fertilization and embryogenesis. The investigation will include: (1) physiological and pharmacological studies on acquisition of fertilizing ability by rhesus spermatozoa, in which the functional correlations between hyperactivated sperm motility, acrosome reactions and penetration of the zona pellucida will be examined; this work will extend previous studies on the stimulation of sperm fertilizing ability by cyclic nucleotide mediators and will also examine the possible role of cumulus oophorus. (2) Studies on the fertilizability of oocytes recovered from normal animals and animals stimulated by gonadotropins or clomiphene, in order to optimize yields of viable oocytes and to examine the steroid profiles of follicles that produce oocytes capable of undergoing fertilization and normal embryonic development; this project will provide information on folliculogenesis and will also facilitate other parts of the program. (3) Attempts to extend development of in vitro fertilized oocytes through all stage of preimplantation embryogenesis and to obtain early post-implantation embryonic growth in vitro in order to provide a primate model for more detailed analyses of these critical phases of development. (4) Transfer of in vitro fertilized rhesus embryos to recipients to obtain offspring and monitoring their post-natal development in order to ascertain if any defects are associated with in vitro fertilization procedures in primates. A project will also be undertaken to ascertain if primate embryos are able to withstand freeze-preservation; if successful, this project would facilitate experimental embryological studies by (e.g.) permitting embryos to be pooled in sufficient numbers to reduce experimental variability, allowing embryos to be transferred to oocyte-donor recipients (autotransfers) following re-establishment of normal menstrual cycles and provide a means for transporting rhesus embryos to other laboratories for breeding purposes or for experimental studies. Taken together, the proposed research will considerably extend knowledge, which is presently very sparse, about primate oocyte development, fertilization and embryogenesis, and may provide new insights into the etiology of embryonic losses and developmental defects in primates.